The present invention relates to a miniature gas turbine engine and, more particularly, to a rotor shaft vibration dampening system which provides dependable sealing and vibration reduction irrespective of long term storage.
Miniature gas turbine or turbojet engines (100 lbf thrust and smaller) are often utilized in single usage applications such as reconnaissance drones, cruise missiles, decoy and other weapon applications, including air-launched and ground-launched weapon systems. The use of such an engine greatly extends the range of the weapon in comparison to the more conventional solid fuel rocket engine. Miniature gas turbine engines are difficult to fabricate economically for general expendable usage in large numbers.
To achieve economically feasible extended range expendable propulsion sources for such applications, it is necessary that the gas turbine engines be manufactured relatively inexpensively yet provide a high degree of reliability and efficiency. One component that greatly affects performance yet is rather complicated to manufacture is the rotating component, such as the rotor system which typically includes a shaft mounted turbine and compressor wheel.
Rotor systems of miniature gas turbine engines typically operate at greater than 100,000 rpm. Such high rotations in the relatively small miniature gas turbine engines may generate high first engine order (1st EO) vibration characteristics that can be damaging to the engine, its vehicle, and/or the payload thereof.
Vibration dampening devices are commonly utilized in relatively large turbomachinery and conventional gas turbine engines. These applications typically operate at relatively lower speeds of below 100,000 rpm. 
As the relatively large applications provide minimal packaging restrictions and are not designed to be expendable, relatively complicated and expensive dampening systems are feasible. As such, conventional dampening devices are impractical and cost prohibitive for miniature gas turbine engines. Heretofore, miniature gas turbine engines avoided most vibration damping systems altogether.
Moreover, known dampening devices typically require periodic maintenance to assure reliability. Such maintenance may be difficult and time consuming particularly for vehicles which are required to be stored for unknown periods prior to usage.
Accordingly, it is desirable to provide a reliable, inexpensive, and uncomplicated dampening system for an expendable gas turbine engine in which long term storage is of minimal concern.